Wave energy has the potential to provide an energy resource in this challenging energyenvironment. Wave energy converters are devices used to extract this energy and convertit into electricity. Wave Carpet is an example of such a novel wave energy converters andin its final form, it consists of a submerged membrane which covers an arbitrarily largearea above the sea floor. Incident waves create a pressure difference between the upper andlower surfaces, which triggers an up-and-down movement. The power take-off attached tothe surfaces serve to restrict this movement and thereby extract hydraulic power which isconverted to electricity.The Wave Carpet, is a type of wave energy converter that is beingdeveloped at University of California Berkeley′s Theoretical and Applied Fluid DynamicsLaboratory (TAFLab).The thesis aims at modeling and designing the different power conversion chainof the entire wave energy converter device. The process of energy conversion that yieldsthe required electrical energy for connecting a wave energy converter to an electricalnetwork is termed as the power conversion chain. A detailed electro-mechanical modelof the wave energy converter system connected to power grid is developed in theMatlab/SIMULINK environment and its corresponding generator and hydraulic controlstructure is implemented. The simulation response of the wave energy converter alongwith the power conversion chain is investigated. / Vågenergi har potential att bli en energiresurs i en utmanande energimiljö. Vågkraftverkär maskiner som används till att utvinna denna energi och omvandla den till elektricitet.Wave Carpet är ett exempel på ett vågkraftverk som i sitt slutglitiga stadie bestårav ett nedsänkt membran som täcker ett godtyckligt stort område ovanför sjöbotten.Inkommande vågor skapar en tryckskillnad mellan den övre och nedre ytan som gerupphov till en lodrätt rörelse. De mekaniska armarna kopplade till membranet bromsardenna rörelse och kan genom hydraulik omvandla bromsenergin till elektricitet. The WaveCarpet är en typ av vågkraftverk som utvecklas vid University of California Berkeley′sTheoretical and Applied Fluid Dynamics Laboratory (TAFLab).Uppsatsen syftar till att modellera och designa effektomvandlingskedjan i ett sådantvågkraftverk. Energiomvandlings processen som ger upphov till elektriciteten via ettvågkraftverk är benämnt som effektomvandlingskedjan. En detaljerad elektro-mekaniskmodell över ett vågkraftverksystem kopplat till ett elnät med motsvarande generator ochhydraliska regulatorer är utvecklad i Matlab/Simulink miljön. Simuleringsresultaten fråndet modellerade vågkraftverket undersöks tillsammans med effektomvandlingskedjan.

Wave energy is a promising renewable resource with a higher energy density than both wind and solar. Waves can travel thousands of kilometers with minimal energy loss, making them more reliable than the previously mentioned alternatives. A device that utilizes wave energy to generate electricity is calleda Wave Energy Converter. The converter studied in this thesis is a non-resonant point absorber, a floating device that absorbs energy through its displacement in the water. An incident wave approaching the converter combined with a latching strategy transforms the wave into a water jet, which emerges as a pulse wave and varies from zero to maximum velocity. The kinetic energy of the water jet gets converted to electricity through a Pelton turbine and a permanent magnet synchronous motor that acts as a generator. The thesis investigates three generator velocity control strategies and two deadtime strategies and aims to answer which strategy yields the best efficiency for the selected wave fields. The strategies strive to maximize the efficiency of the Pelton turbine while minimizing the frictional and electrical losses. The first velocity control approach relies on historical data and computes the average based on the previous wavefield. The second approach maintains a predetermined turbine velocity based on the average jet velocity of each incident wave. Lastly, the third strategy continuously adapts the speed during each jet pulse to maximize the Pelton turbine efficiency. The dead-time strategies refer to the approaches employed between waves. The first approach maintainsa constant generator velocity, reducing the necessary acceleration to match the next incident wave. The second approach freewheels the generator, allowing it to decelerate due to friction losses. During the deceleration, the generator draws no current, but as the next wave arrives it must instead accelerate. Consequently, drawing more current but during a shorter period. The results reveal that there is no significant difference between the two deadtime strategies, but there is a significant difference between the velocity control strategies. Furthermore, the results illustrate the effectiveness of the local averaging method and the adaptive control method, which result in the highest system efficiency. / Vågenergi är en lovande energiresurs som har högre energidensitet än både vind- och solkraft. Vågor kan färdas tusentals kilometer med minimal energiförlust,vilket gör dem mer tillförlitliga än de tidigare nämnda alternativen. En anordning som kan nyttja vågors energi för att generera elektricitet kallas för vågenergiomvandlare. Omvandlaren som studerats i detta arbete är en icke-resonant punktabsorbent,vilket är en flytande anordning som absorberar energi genom dess förflyttning i vattnet. När en kommande våg närmar sig omvandlaren transformeras vågen till en vattenstråle, som framträder som en pulsvåg och varierar mellan noll och maxhastighet, via en styrstrategi vid namn ”latching”. Den kinetiska energin från vattenstrålen omvandlas till elektrisk energi via en Peltonturbin och en synkronmotor som agerar som generator. Det här arbetet undersöker tre hastighetsstyrstrategier samt två mellantidsstrategier för generatorn, och ämnar besvara vilken som är den mest effektiva strategin för en uppsättning vågor. Målet med dessa strategier är att maximera effektiviteten hos Peltonturbinen medan friktions- samt elektriska förluster minimeras. Den första hastighetsstyrstrategin håller en konstant hastighetbaserad på ett medelvärde från ett tidigare vågfält. Den andra strategin hålleren konstant hastighet, vilken anpassas till varje inkommande våg. Den tredje strategin anpassar hastigheten kontinuerligt under pulsvågen för att maximera turbineffektiviteten. Med mellantidsstrategierna menas de styrstrategier som nyttjas mellan vattenpulserna. I den första mellantidsstrategin körs generatorn som motor och håller konstant hastighet, vilket minskar de nödvändiga accelerationerna för att möta kommande vågs referenshastighet. Den andra strategin låter generatorn frihjula, vilket gör att hastigheten faller på grund av friktionsförluster. Under hastighetsminskningen drar generatorn ingen ström, men den måste då istället accelerera när kommande våg anländer. Detta innebär att generatorn kommer att dra mer ström, men under en kortare period. Resultaten avslöjade att det inte var någon signifikant skillnad mellan de två mellantidsstrategierna och att det var en signifikant skillnad mellan hastighetsstyrstrategierna. Resultatet visade att de två metoderna med variabel hastighet gav högre systemeffektivitet än metoden med konstant hastighet.

<p>У тези je предложен поступак развоја управљачких склопова енергетске<br />електронике заснован на технологији Hardware In the Loop. Подробно је<br />описан предложени емулатор са нагласком на специфичном<br />моделовању погодном за извршење у стварном времену што је<br />предуслов веродостојности. Сама веродостојност је проверена<br />поређењем резултата са симулацијом, као и са измереним резултатима<br />у неколико стварних погона. Затим је поступак развоја управљачких<br />склопова подробно објашњен на примеру развоја и испитивања једног<br />новог контролног алгоритма за повезивање синхроног генератора на<br />електричну мрежу.</p> / <p>U tezi je predložen postupak razvoja upravljačkih sklopova energetske<br />elektronike zasnovan na tehnologiji Hardware In the Loop. Podrobno je<br />opisan predloženi emulator sa naglaskom na specifičnom<br />modelovanju pogodnom za izvršenje u stvarnom vremenu što je<br />preduslov verodostojnosti. Sama verodostojnost je proverena<br />poređenjem rezultata sa simulacijom, kao i sa izmerenim rezultatima<br />u nekoliko stvarnih pogona. Zatim je postupak razvoja upravljačkih<br />sklopova podrobno objašnjen na primeru razvoja i ispitivanja jednog<br />novog kontrolnog algoritma za povezivanje sinhronog generatora na<br />električnu mrežu.</p> / <p>This paper proposes development of Power Electronics controllers based on<br />the Hardware In the Loop technology. Proposed emulator is describied in<br />detail where emphasis was set on specific methods of modeling which is<br />suitable for real time emulations in order to obtain emulation faithfulness.<br />Fidelity itself was checked through comparison with off-line simulations and<br />results of real drives. Procedure of controllers development was presented<br />through development and testing of one new control algorithm for connection<br />of the permanent magnet synchronous generator to the electrical grid.</p>

Small signal oscillation has been always a major concern in the operation of power systems. In a generator, the electromechanical coupling between the rotor and the rest of the system causes it to behave in a manner similar to a spring mass damper system. Following any disturbance, such as sudden change in loads, actuations in the output of turbine and faults etc. it exhibits an oscillatory behaviour around the equilibrium state. The use of fast acting high gain AVRs and evolution of large interconnected power systems with transfer of bulk power across weak transmission links have further aggravated the problem of these low frequency oscillations. Small oscillations in the range of about 0.1Hz to 3.5Hz can persist for long periods, limiting the power transfer capability of the transmission lines. These oscillations can be reduced by incorporating auxiliary controllers on generator excitation system. Power System Stabilizers (PSSs) were developed to produce additional damping by modulating the generator excitation voltage. Designing effective PSS for all operating conditions especially in large interconnected power systems still remains a difficult and challenging task. More and more power electronic based controllers have been and will be used in power systems. Many of these controllers such as Static Var Compensators (SVCs), Static Synchronous Compensators (STATCOMs) and Unified Power Flow Controllers (UPFCs) etc., are incorporated in power transmission networks to improve its operational capability. In addition, some of the energy storage systems such as Battery Energy Storage systems (BESS), Super conducting Magnetic Energy Storage System (SMES) as well large non-conventional energy sources are also increasingly being integrated with the power grid. With large integration of these devices, there is a significant impact on system stability, more importantly on small signal oscillatory instability of the power system. This thesis primarily focuses on impact of such devices on small signal oscillatory stability of the power systems. More specifically in this thesis small signal stability analysis of a Single Machine Infinite Bus (SMIB) system with a grid connected wind powered Permanent Magnet Synchronous Generator (PMSG) has been presented. A SMIB system has been purposely chosen so that general conclusions can be obtained on the behaviour of the embedded STATCOM/Energy Source (ES) system on system stability. With a better understanding of the impact of such a system it would be probably possible to analyze more complicated multimachine power system and their impact on system stability. Small signal model of the complete system which comprises the generator, transmission network, inter connecting STATCOM, the wind power generator and all associated controllers has been developed. The performances of the system following a small disturbance at various operating conditions have been analyzed. To obtain quantitative estimates of the damping and synchronizing torques generated in the system, expressions for damping and synchronizing torque clients have been developed. With these analyses, the relative impact of the STATCOM and STATCOM with ES on system performance have been assessed. It is shown that with active and reactive power modulation capabilities effective and efficient control of small signal oscillations in power systems can be achieved.

Les Éoliennes à Entraînement Direct (ÉED) sont équipées de Générateurs Syn- chrones à Aimants Permanents (GSAP). Leurs trois plus courantes défaillances sont la dé- magnétisation, l’excentricité (statique, dynamique et mixte) et le court-circuit inter-tour. L’analyse de la signature du courant de la machine est souvent utilisée pour rechercher des problèmes du générateur, car ces altérations introduisent des harmoniques supplémen- taires dans les courants générés. La Transformée de Fourier Rapide (TFR) est utilisée pour calculer le spectre des courants. Cependant, la TFR permet de calculer l’ensemble du spec- tre, tandis que le nombre de défauts possible et le nombre d’harmoniques introduites sont faibles. L’algorithme de Goertzel, mis en oeuvre sous forme de filtre (le filtre de Goertzel), est présenté comme une alternative plus efficace au TFR. Le spectre des courants change avec la vitesse du vent, ce qui rend la détection plus difficile. Le Filtre de Kalman Étendu (FKÉ) est proposé comme solution. Le spectre de résidus, calcule entre les courants estimés et les courants générés, est constant, quelle que soit la vitesse du vent. Cependant, l’effet des défauts est visible dans leur spectre. Lors de l’utilisation de l’FKÉ, un défi consiste à estime la matrice de covariance pour le bruit du processus. Une nouvelle méthode était développée pour ça, qui n’utilise aucune de maîtrise du filtre. Les ÉED sont placés soit dans des zones éloignées, soit dans des villes. Pour la surveillance des ÉED, des dizaines ou des centaines de kilomètres de câbles sont nécessaires. Les Réseaux de Capteurs sans Fil (RCF) sont bien adaptés pour être utilisés dans l’infrastructure de communication des ÉED. RCF ont des coûts initiaux et d’entretien plus faibles et leurs installations sont rapides. De plus, ils peuvent compléter les réseaux câblés. Différentes technologies sans fil sont comparées : les technologies à grande surface, ainsi que les technologies à courte portée qui supportent des débits de données élevés. / Direct Drive Wind Turbines (DDWTs) are equipped with Permanent Magnet Syn- chronous Generators (PMSGs). Their three most common failures are demagnetization, ec- centricity (static, dynamic and mixed) and inter-turn short circuit. Machine Current Signa- ture Analysis is often used to look for generator problems, as these impairments introduce additional harmonics into the generated currents. The Fast Fourier Transform (FFT) is utilized to compute the spectrum of the currents. However, the FFT calculates the whole spectrum, while the number of possible faults and the number of introduced harmonics is low. The Goertzel algorithm, implemented as a filter (the Goertzel filter), is presented as a more efficient alternative to the FFT. The spectrum of the currents changes with the wind speed, and thus the detection is made more difficult. The Extended Kalman Filter (EKF) is proposed as a solution. The spectrum of the residuals, computed between the estimated and the generated current, is constant, regardless of the wind speed. However, the effect of the faults is visible in the spectrum. When using the EKF, one challenge is to find out the covariance matrix of the process noise. A new method was developed in this regard, which does not use any of the matrices of the filter. DDWTs are either placed in remote areas or in cities. For the monitoring of a DDWT, tens or hundreds of kilometers of cables are necessary. Wireless Sensor Networks (WSNs) are suited to be used in the communication infrastructure of DDWTs. WSNs have lower initial and maintenance costs, and they are quickly installed. Moreover, they can complement wired networks. Different wireless technologies are com- pared - both wide area ones, as well as short range technologies which support high data rates.